Thickness dependence of AC conductivity in TlSe thin films

Thalium selenide (TlSe), which has a lattice with tetragonal symmetry, is a member of the A(3)B(6) semiconductor group. The structure of TlSe is defined as chains where atoms inside are bonded with an ionic-covalent bond. TlSe thin films were deposited by thermal evaporation under a high vacuum on glass substrates. The structure of TlSe thin films is amorphous with a tetragonal structure. The AC conductivity measurements were operated via the measurements of capacitance and dielectric dissipation (tan delta) at room temperature. AC conductivity values change between 10(-11) and 10(-6) S/cm at the low-frequency side with decreasing thickness. Two different conduction regions were observed with increasing frequency. The region observed at the low-frequency side can be attributed to the motion of a chain-like part of the lattice, while the region observed at the high-frequency side can be attributed to side groups.